package algocasts;

public class P18_mergeTwoSortedLists {
    class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }
    // Time:O(m+n)  Space:O(1)
    public ListNode mergeTowSortedLists(ListNode l1, ListNode l2) {
        ListNode dummy = new ListNode(0), p = dummy;
        while (l1 != null && l2 != null) {
            if (l1.val < l2.val) {
                p.next = l1;
                l1 = l1.next;
            } else {
                p.next = l2;
                l2 = l2.next;
            }
            p = p.next;
        }
        if (l1 != null) p.next = l1;
        if (l2 != null) p.next = l2;
        return dummy.next;
    }
}
